#include <stdio.h>

/* 全局变量声明 */
int g;

int main() {
    /* 局部变量声明 */
    int a, b;

    /* 实际初始化 */
    a = 10;
    b = 20;
    g = a + b;

    printf("value of a = %d, b = %d and g = %d\n", a, b, g);

    return 0;
}